時効硬化性 Fe-16Ni-4Si 合金の時効前組織と引張特性

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An Fe-16%Ni-4%Si alloy having a large hardenability due to a maraging mechanism was used to study the effect of microstructures prior to aging upon the strength properties under a tensile test. In contrast to the conventional solution treatment for maraging steels in the γ field, the present alloy was cold rolled by 80% at a martensite state (marforming) and annealed at the temperatures in the α+γ two-phase range before aging, in an attempt to obtain microduplex structures showing a good combination of strength and toughness. The marforming was found to increase both the tensile strength, σ_u, and the reduction of area, φ, due to the formation of proper duplex structures. In case, annealing was made at the temperatures around 570℃, large uniform elongation, ε_u, was observed due to a transformation plasticity of austenite which was formed on the annealing and would be rich in Ni, but the strength, σ_u=120kg/mm^2, was rather low. In case, annealing was carried out at the temperatures from 600 to 650℃ (still in the two-phase field), the reverted austenite was transformed on cooling into martensite which in turn was strengthened by aging proportionally to the martensite fraction ; the resultant duplex structure had a strength of σ_u=158kg/mm^2, and a plasticity of φ=27% and ε_u=1%, which were better than thd combination, σ_u=132kg/mm^2, φ=25% and ε_u=1% in the same alloy that was conventionally age-hardened without marforming and annealing. The marforming had a dominant effect on the reduction of transgranular brittle fracture as well as intergranular fracture associated with large austenite grains which had been present prior to the annealing in the two-phase range.
社団法人日本鉄鋼協会の論文
1980-01-01

時効硬化性 Fe-16Ni-4Si 合金の時効前組織と引張特性

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